1. Field
This invention relates to the field of antiviral compounds and compositions for the treatment against flaviviral infections. More specifically, it relates to N-pentyl-(1-hydroxycyclohexyl)-DNJ derivatives and their use as pharmaceutical compositions in the treatment and prevention of Dengue, West Nile, Japanese Encephalitis virus, Bovine viral diarrhea virus, and hepatitis C.
2. Background Art
Imino sugars are broad-spectrum antiviral agents that interfere with virus assembly through glucosidase inhibition. Dengue virus has an envelope protein with a specific structure that makes it more sensitive to imino sugar treatment. Consistent with this notion is the observation that virion production of many types of enveloped viruses, including hepatitis B virus, human immunodeficiency virus, herpes simplex virus-1, influenza viruses, parainfluenza virus, measles virus as well as several members of flaviviridae family, such as bovine viral diarrhea virus (BVDV), dengue virus (DV), West Nile virus (WNV), Japanese encephalitis virus (JEV) and hepatitis C virus, can be inhibited by α-glucosidases inhibitors, such as deoxynojirimycin (DNJ) and its derivatives.
As a substrate analog, some imino sugar derivatives can competitively inhibit the activity of α-glucosidases I and II in endoplasmic reticulum (ER). ER α-glucosidases are enzymes that catalyze the first step trimming of glucose from the high-mannose N-linked glycan structure attached to the nascent glycoproteins. Proper processing of the terminal glucose residues from N-linked glycans is critical for the subsequent interaction between glycoprotein and ER chaperones calnexin and calreticulin. For some, but not all of the glycoproteins, this interaction is required for the correct folding and sorting. Thus, inhibition of α-glucosidases leads to the misfolding and degradation of glycoproteins where this specific interaction is required.
Viral envelope proteins are usually glycoproteins. It has been shown that for many types of enveloped viruses, such as hepatitis B virus, human immunodeficiency virus, herpes simplex virus 1 as well as several members of flaviviridae family, their viral envelope glycoproteins depend on the calnexin/calreticulin mediated folding pathway. Thus alteration of glycan structure on envelope protein by an α-glucosidase inhibitor such as imino sugars interfere with the maturation of viral envelope proteins, and as a consequence, viral particle assembly and/or secretion can be inhibited. In some cases, viral particles carrying altered glycan structure also demonstrated reduced infectivity. Therefore, glucosidase inhibitors are applicable as broad spectrum antivirals against many types of enveloped viruses.
Folding and maturation of envelope proteins of flaviviruses are extremely sensitive to glucosidase inhibition. Antiviral activity of imino sugars has been shown for both in vitro and in vivo experiments, against Dengue virus (DV), West Nile virus (WNV) and Japanese encephalitis virus (JEV). Recently, another member of flaviviridae, hepatitis C virus (HCV), was shown to be sensitive to imino sugar treatment in tissue culture. In many studies, Bovine Viral Diarrhea Virus (BVDV), which belongs to pestivirus of flaviviridae has been used as model system for flavivirus such as DV and WNV, as well as HCV.
The development of a imino sugar glucosidase inhibitor is limited by low efficacy and/or cytotoxicity. The prototype imino sugar, deoxynojirimycin (DNJ), requires millimolar concentrations to achieve 50% inhibition in virus yield reduction assays (EC50). Modification of DNJ by adding alkylated side chains on the nitrogen atom, improved antiviral efficacy. For example, N-nonyl-DNJ (NNDNJ), which is a DNJ derivative with a nine-carbon alkyl side chain, reduced EC50 to a lower micromolar level. However, NNDNJ also showed higher cytotoxicity. Hence, the present invention describes a chemical modification on the nitrogen linked alkylated side, chain to improve both efficacy and cytotoxicity profiles.
Generally, hemorrhagic fever viruses (HFV) are a group of diseases, caused by enveloped, single-stranded RNA viruses from four different virus families, that are acquired through contact with animals or the bite of an infected arthropod. Table 1 summarizes viruses from these four families that are included in NIAID category A of potential bioterror agents.
TABLE 1Summary of NIAID category A agents that cause VHFFamilyGenomevirusFatalityVirionsClinical feature/PathogenesisFiloviridaeNon-segmentedEbola virus (Zaire)60-90%EnvelopedDisseminated intravascularNegative-senseMarburg23-70%with glycosylatedcoagulation (DIC)ArenavirideBi-segmentedJunin virus/Machupo virus15-30%viralBleeding/ThombocytopeniaNegative-senseGlycoprotein(s)Lymphocyte(Ambisense)Apoptosis/DepletionBunyaviridaeTri-segmentedHantavirus 5-15%Macrophage infectionNegative-senseRift Valley Fever virus1%Dendritic Cell infection(Ambisense)Cytokine tsunamiFlaviviridaeNon-segmentedDengue virus1-5%Positive-sense
More specifically, Dengue virus (DV) infection is a growing world health problem and a bio-terror concern. DV is mosquito-borne flavivirus that causes lethal hemorrhagic fever in people. The global burden of dengue has grown dramatically in recent decades, and it is currently classified as a re-emerging infectious diseases. Dengue fever (DF) and dengue haemorrhagic fever (DHF)/dengue shock syndrome (DSS) occur in over 100 countries, with more than 2.5 billion people at risk and an estimated 50 million infections each year with 500,000 hospitalized cases and 25,000 deaths. Although the major disease burden is mainly found in the tropical/sub-tropical regions of south-east Asia and the western Pacific, with globalization of the world accompanied by gradual shift in global climate, there are increased reports of dengue related diseases in America and other developed countries. Moreover, due to the feature of dengue virus to grow in high titer in cell culture and the infectability in aerosol form, it has been identified as one of the priority concern for bio-terror control.
Thus far, effective antiviral therapies and vaccines are not yet available to treat or prevent DV infection. For the control of DV infection, in addition to better insecticides, rapid diagnostics, safe vaccine, it seems likely that strategic use of antivirals, during periods of viremia, would be beneficial. DHF and DSS are considered to directly correlate with higher titer of viremia, therefore, antivirals that can lower viral load by 2 logs or greater are anticipated to reduce serious dengue diseases, decrease mortality associated with pandemic and slow down transmission.
Chemotherapy against dengue virus infection can be developed by two principally different approaches, blocking the virus coded functions or the cellular functions needed for virus replication. Although targeting host functions has the potential to hamper normal cellular activity, it is advantageous in the way that the therapy may be active against many viruses using similar pathway. Moreover, the emergence of resistant virus would be expected to be rare. Recently, antivirals targeting the host factors become more attractive, since some treatments, such as the one we proposed using imino sugar targeting host glucosidase, demonstrated high selectivity against virus over cellular function, especially for short period of treatment during acute virus infection such as dengue infection.
Previously the imino sugar derivative N-pentyl-(1-hydroxycyclohexyl)-DNJ (OSL-95II) has been identified as having micromolar antiviral activity (US 2009/0042268, incorporated by reference in its entirety). Compared to NNDNJ, OSL-95II has reduced cytotoxicity but retains micromolar antiviral activity against BVDV, DV and WNV infection. The characteristic feature of OSL-95II is a 5-carbon alkylated side chain with a terminal ring structure. In the present invention, OSL-95II is modified by changing the length and/or composition of nitrogen linked side chain, resulting in a new structural type of imino sugars with not only better toxicity profile, but also superior antiviral activity against BVDV, DV and WNV infection. For DV infection, the present invention provides imino sugar derivatives having EC90 values in submicromolar concentration indicating their potential to be candidate for further clinical development as therapeutic agents.